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**philhguk** · 13-04-2013, 05:52 PM

Re: Rudder sensitivity

Have you done the rudder servo endpoint setting on the 3gx

**TheDarkPassenger** · 13-04-2013, 05:57 PM

I'm pretty sure I have.

It's where you go left until the slider reached the end, return to centre, wait for red light to flash, then repeat to the right?

Is that right?

(Originally I was doing it and letting the servo travel until it physically stopped, which seemed to be over-doing it and the result was that the link was binding.)

**vinny155** · 13-04-2013, 06:03 PM

im pretty sure thats ok on the deck?should be different in the air,have you tried spooling it up on the deck and giving rudder?

**philhguk** · 13-04-2013, 06:04 PM

Re: Rudder sensitivity

Originally posted by TheDarkPassenger View Post

I'm pretty sure I have.

It's where you go left until the slider reached the end, return to centre, wait for red light to flash, then repeat to the right?

Is that right?

(Originally I was doing it and letting the servo travel until it physically stopped, which seemed to be over-doing it and the result was that the link was binding.)

yes I had a lot of problems with that so I did it so it was just at the end rather than waiting for it to stop.

if you look up my username you will find a few posts in the last few days about my trex 250 3gx setup there is a link in the tail spinning thread that links to another thread that has a really good setup guide for the 3gx

**philhguk** · 13-04-2013, 06:12 PM

Oh yes make sure you do the full tail setup including the servo speed and type and the gyro reverse etc.

Someone post a video on one of my threads that helped me massively here it is watch it and make sure you have done all the steps as it worked for me.

Here is the video:

**tomatwalden** · 13-04-2013, 08:15 PM

You can change it using dual rates. I noticed the same thing ages ago when I configured my Trex500 with my DX6i. On the bench it worried me, and I adjusted it out by using DR on the tail. Fundamentally though, I finally realised that there's nothing wrong, and I removed the DR.

The thing to remember is this ... The rudder is gyro-controlled, through the FBL unit. Your rudder input on the TX is telling the heli to move, not the tail servo. On the bench therefore, you give a rudder input and the FBL unit detects no change in the heli orientation ... ergo, it gives MORE input, until it reaches the full limit.

In short, there's probably nothing wrong! Get it flying, try the tail gently at first and see how it feels in flight.

Don't try to tune it on the bench!

**TheDarkPassenger** · 13-04-2013, 09:09 PM

Thanks all, very helpful advice, appreciated.

My 1st build, so these things are new to me, never know whether to be worried or not.

I must have gone through the 3GX setup at least 5 times now and have missed something every time, we'll get there in the end

**franky975** · 13-04-2013, 09:26 PM

Just make sure at take off you don't touch the cyclic stick before the heli leaves the deck as same thing happens on aileron/elevator if you do. If you give input to the 3gx it gives command to the servos BUT since the heli not airborn yet will happend no changes in its position therefore the 3gx will give more and more commant to the servo untill it flips over and crashes. I usually stop on spoil up for 4-5 second just below hovering stick position and lift my thumb off from the stick to make sure i don't give command and give time to the controller to go back to zero swash position.

**tomatwalden** · 13-04-2013, 09:53 PM

Originally posted by franky975 View Post

Just make sure at take off you don't touch the cyclic stick before the heli leaves the deck as same thing happens on aileron/elevator if you do. If you give input to the 3gx it gives command to the servos BUT since the heli not airborn yet will happend no changes in its position therefore the 3gx will give more and more commant to the servo untill it flips over and crashes. I usually stop on spoil up for 4-5 second just below hovering stick position and lift my thumb off from the stick to make sure i don't give command and give time to the controller to go back to zero swash position.

This was very true with early versions of the Align 3G and versions up to v1.2 of the 3GX. From 2.1, 3.0 and 3.1 however, the tipping on take off has been vastly improved, and unless you give very strong inputs, tip over on take off shouldn't really happen. As a general rule of thumb however, minimal cyclic input on the ground is still good advice however.

**franky975** · 13-04-2013, 10:27 PM

I don't have experience with align fbl controllers as i have beastx and brain on my helis. I just wanted to point it out in general with flybarless.

**coolice** · 13-04-2013, 11:20 PM

Originally posted by tomatwalden View Post

You can change it using dual rates. I noticed the same thing ages ago when I configured my Trex500 with my DX6i. On the bench it worried me, and I adjusted it out by using DR on the tail. Fundamentally though, I finally realised that there's nothing wrong, and I removed the DR.

The thing to remember is this ... The rudder is gyro-controlled, through the FBL unit. Your rudder input on the TX is telling the heli to move, not the tail servo. On the bench therefore, you give a rudder input and the FBL unit detects no change in the heli orientation ... ergo, it gives MORE input, until it reaches the full limit.

In short, there's probably nothing wrong! Get it flying, try the tail gently at first and see how it feels in flight.

Don't try to tune it on the bench!

Hey.

Tom's description is spot on.
What happens with modern HH gyros and FBL gyros now controlling the cyclic, is that you are not movign the control surfaces directly, but merely asking for a specific flip/roll/yaw rate of rotation in degree's per second. Hence on the ground a small control input yields a large control surface movement as the FBL unit is not detecting any movement and so throws in even more control command to effect a change.
This is why the problems can occur on take off with the skids still in contact with the ground, any cyclic changes do not effect the model and so the FBL unit throws in even more control movment and you run the risk of tip overs.
In my experience I found that the smaller models suffered with problems more than larger machines, the best advice is the keep any cyclic commands to a minimum on take off.
.

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